PCR-based microsatellite analysis to accelerate diabetogenic genetic background acquisition in transgenic mice

The Non-obese diabetic (NOD) mice exhibit a susceptibility to spontaneous development of autoimmune diabetes and is the most widely used experimental model for the study of the disease. The NOD strain was established by inbreeding in 1980. This model has a MHC-matched diabetes resistant homologous, NOR/Lt mice, an insulitis-resistant and diabetes-free strain produced from an isolated genetic contamination within a NOD/Lt line. To evaluate the role of transgenes, transgenic mice can be generated in CD-1 mice for technical advantages and then backcrossed to inbred strains. To obtain transgenic mice in NOD or NOR background starting from CD-1, at least 20 backcrosses are required, spending more than two years in the process.

Nucleotide repeats (microsatellites) mapped to specific locations on each chromosome are used to evaluate genomic polymorphism. From 23 microsatellites we selected eleven that were variant in PCR amplimer size between CD-1 colony and NOD or NOR strains. We used these microsatellites to identify individuals that were used for backcrossing, thus accelerating the acquisition of a new genetic background. Results yield a defined analysis of the genome in question and profiles were compared to detect genetic variation among individuals. After the selection of mice for backcrossing at the third generation, the 11 specific markers were acquired at the 5th generation and maintained to the 10th generation. Diabetes incidence and insulitis score correlated with the acquisition of genetic background, demonstrating that using this strategy, 5–6 crosses are enough to obtain the genotype of interest, shortening the process in more than one year and a half.